The present invention relates to devices for injecting, administering, infusing, delivering or dispensing a substance, and to methods of making and using such devices. More particularly, it relates to injection devices for administering a liquid product such as a medicinal substance or a medicament and, more particularly, to an injection device and a method of moving or retracting a needle associated with the injection device from a piercing position in a controlled manner.
A known utilization or method of use of injection devices, including automatic injectors, is for a needle to be injected in a patient by a mechanism of the device, after which the product is administered to the patient through the needle. After the product has been successfully dispensed, the needle is covered and/or pulled back into the injection device.
For example, U.S. Pat. No. 6,387,078 discloses an injection device in which a needle firstly effects a piercing movement with the aid of a driving spring and the product is then dispensed by the urging of the driving spring. As the driving spring moves forward, a return spring is simultaneously tensed. Immediately on reaching the end position of a dispensing movement, the driving spring is uncoupled from the return spring so that the return spring immediately retracts or moves the needle back into the housing. As this happens, it may be that the medicament is not or has not been completely injected into the patient's tissue and a small amount is lost. This is annoying, especially in the case of expensive drugs. The amount that is lost can also lead to problems with respect to the actual dose administered.